Photofinishers customarily employ one or more quality control tools, typically in the form of calibrated first-generation camera-original negatives that contain reference portrait images, to make comparison measurements or observations in order to "fine tune" the operation and performance of various pieces of photofinishing equipment. (These calibrated camera-original negatives have come to be referred to as "Shirleys", named after the model photographed during the initial production many years ago).
The graphic art industry has also recognized a need for calibrated camera-original photographs to be used in controlling the operation and performance of their equipment.
Because the contents of these camera-original reference negatives must be specified to extremely high standards, the process conventionally employed to produce them is expensive, labor intensive and time consuming. Some of the same considerations may apply even when the scene does not contain a live model but is comprised of inanimate objects such as color charts.
For the purpose of clarity throughout this document, definitions of the following terms as they will be used throughout this discussion are given below.
The term "negative" will refer to a camera exposure onto a film type from which photographic paper prints are normally produced.
generally speaking, the photographic terms "positive" and "transparency" are interchangeable. For the sake of clarity, in this discussion the term "positive" will be reserved to mean a camera-original exposure onto a reversal film type, from which photographic paper prints are not normally produced, but which are usually viewed via projection.
The term "transparency", will be used to mean that computer-originated image (defined below) which is digitally-generated using a digital output recording device onto a photographic or other non-photographic (e.g., thermal) medium and which is intended to be illuminated and photographed or otherwise captured to produce "second-generation camera-original" exposures, (defined below), whether onto a negative or positive film type or other recording medium. The computer-originated image need not be on a reversal film type, but may be digitally output as a reflection print.
The term "first-generation camera-original" will refer to a photographic exposure that is created in the usual manner, using a conventional camera to photograph a live scene. This camera exposure may be photographed onto either a negative or a positive film type.
The term "computer-originated image" will refer to an image which does not originate as a "live scene", in the conventional sense, but which is digitally created using any one of several computer artwork, computer aided design or digital image rendering software programs. Such images are usually composed of digital picture elements ("pixels") whose values can be stored in the form of a digital data file in a "primary metric" (defined below).
The term "second-generation camera-original" will refer to a photographic exposure that is created using the method embodied within the present invention wherein a transparency produced by a digital output recording device is backlit and photographed using a conventional camera. A second-generation camera-original exposure may be photographed onto either a negative or a positive film type. This term will also include other methods of recording the output of the digital output recording device, such as enlarging. Also, the output of the digital output recording device can be on a medium other than a transparency, such as print paper.
The term "product film type" will refer to that film type or other medium (e.g., thermal) onto which second-generation camera-original product control tool photographs of an illuminated digitally-generated transparency of a computer-originated image are exposed or otherwise captured.
Since second-generation camera-original exposures may be produced on either a negative or positive film type, the term "photograph" will be used to avoid the cumbersome phrase "negative (or positive)" throughout the document.
The term "primary metric" will be used as an abbreviation for the more cumbersome phrase "primary digital image data metric."
The term "target metric" will be used as an abbreviation for the more cumbersome phrase "secondary, target digital image data metric."
The term "develop" will refer to the photochemical processing of an exposure, whether the exposure was created via a camera, a photographic enlarging device, a digital output device or other exposing device.
The term "image characteristics" will be used to minimize the cumbersome phrase "tone, color and frequency response characteristics" throughout. In places where the full phrase lends clarity, the full phrase will appear.